In the field of Micro-Electro-Mechanical Systems (MEMS), devices may use or include extremely small mechanical devices. For example, in current MEMS technologies, a Film Bulk Acoustic Resonator (FBAR) Radio Frequency (RF) filter includes a thin membrane and a support substrate, for example, a silicon substrate.
Certain MEMS devices, for example, FBAR filters that comply with RF communication specifications, e.g., insertion loss specifications, require minimizing loss of RF energy during operation. In such devices, RF energy may be lost due to undesired parasitic capacitance between metal conductors of the FBAR RF filter and its silicon substrate during operation of the filter. Such conductors may pass on top of the silicon substrate of the filter, and may be separated from the silicon substrate by a thin dielectric layer, for example, epoxy glue or a similar polymer. The undesired parasitic capacitance, which may be caused by the relatively high conductivity of both the metal and the silicon, is often a significant contributor to the overall energy loss of the filter.
To somewhat reduce energy loss, certain MEMS devices, for example, certain FBAR RF filters, may be produced from high-resistance silicon instead of standard silicon. However, high-resistance silicon is significantly more expensive than conventional silicon.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.